The new version is built on our C2 rim extrusion. C2 is alloyed with Scandium, which makes it lighter than the old version, which is nice; but what really excites us is what a wider rim does to the tire.
On a 23mm wide rim, the tire beads are farther apart and the tire profile is shorter and rounder. Put a 20 or (especially) a 23mm tire on a 19mm rim and the resulting profile looks more or less like a lightbulb. Even with an aero rim behind it, the wind still "sees" a bulb at both ends of the wheel. On the C2 wheels, a 20mm tire looks like a bullet, and even a 23 does not hang over the brake surface. The wind "sees" a smoother shape. The result is that you are faster.